In the short term, don't worry about putting anyone off visiting the USA, the idiot dollar spending vacationer will still come, there is lot's to see and do. I'd be more worried about business and academic visitors, though only a small amount of revenue is lost per individual or event canceled, 20 years of finding somewhere better for that conference or supplier meeting or University to study/endow/partner with will make for interesting outcomes. Even the cattle class visitors will notice in the end.

I have for years postulated a big enough event say, a large hurricane that tears up the expensive parts of the east coast of the USA, might be enough to prompt some serious thought about climate change, but Sandy was not really big enough, only 50B worth of costs, I guess it will take a really big one to carve up Florida or Washington DC to prompt a reaction. Let's face it either it's a freak event (or two or three), Global climate change, or God hates you.